range coder

Originally committed as revision 3654 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 178 insertions, 0 deletions

diff --git a/libavcodec/rangecoder.c b/libavcodec/rangecoder.c
new file mode 100644
index 0000000000..159607c652
--- /dev/null
+++ b/libavcodec/rangecoder.c
@@ -0,0 +1,178 @@
+/*
+ * Range coder
+ * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+ 
+/**
+ * @file rangecoder.c
+ * Range coder.
+ * based upon
+ *    "Range encoding: an algorithm for removing redundancy from a digitised
+ *                     message.
+ *     G. N. N. Martin                  Presented in March 1979 to the Video &
+ *                                      Data Recording Conference,
+ *     IBM UK Scientific Center         held in Southampton July 24-27 1979."
+ *
+ */
+
+#include <string.h>
+
+#include "avcodec.h"
+#include "common.h"
+#include "rangecoder.h"
+
+
+void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){
+    c->bytestream_start= 
+    c->bytestream= buf;
+    c->bytestream_end= buf + buf_size;
+
+    c->low= 0;
+    c->range= 0xFF00;
+    c->outstanding_count= 0;
+    c->outstanding_byte= -1;
+}
+
+void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){
+    ff_init_range_encoder(c, buf, buf_size);
+
+    c->low =(*c->bytestream++)<<8;
+    c->low+= *c->bytestream++;
+}
+
+void ff_build_rac_states(RangeCoder *c, int factor, int max_p){
+    const int64_t one= 1LL<<32;
+    int64_t p;
+    int last_p8, p8, i, j;
+
+    memset(c->zero_state, 0, sizeof(c->zero_state));
+    memset(c-> one_state, 0, sizeof(c-> one_state));
+
+#if 0
+    for(i=1; i<256; i++){
+        if(c->one_state[i]) 
+            continue;
+        
+        p= (i*one + 128) >> 8;
+        last_p8= i;
+        for(;;){
+            p+= ((one-p)*factor + one/2) >> 32;
+            p8= (256*p + one/2) >> 32; //FIXME try without the one
+            if(p8 <= last_p8) p8= last_p8+1;
+            if(p8 > max_p) p8= max_p;
+            if(p8 < last_p8)
+                break;
+            c->one_state[last_p8]=     p8;
+            if(p8 == last_p8)
+                break;
+            last_p8= p8;
+        }
+    }
+#endif
+#if 1
+    last_p8= 0;
+    p= one/2;
+    for(i=0; i<128; i++){
+        p8= (256*p + one/2) >> 32; //FIXME try without the one
+        if(p8 <= last_p8) p8= last_p8+1;
+        if(last_p8 && last_p8<256 && p8<=max_p)
+            c->one_state[last_p8]= p8;
+        
+        p+= ((one-p)*factor + one/2) >> 32;
+        last_p8= p8;
+    }
+#endif
+    for(i=256-max_p; i<=max_p; i++){
+        if(c->one_state[i]) 
+            continue;
+
+        p= (i*one + 128) >> 8;
+        p+= ((one-p)*factor + one/2) >> 32;
+        p8= (256*p + one/2) >> 32; //FIXME try without the one
+        if(p8 <= i) p8= i+1;
+        if(p8 > max_p) p8= max_p;
+        c->one_state[    i]=     p8;
+    }
+    
+    for(i=0; i<256; i++)
+        c->zero_state[i]= 256-c->one_state[256-i];
+#if 0
+    for(i=0; i<256; i++)
+        av_log(NULL, AV_LOG_DEBUG, "%3d %3d\n", i, c->one_state[i]);
+#endif
+}
+
+/**
+ *
+ * @return the number of bytes written
+ */
+int ff_rac_terminate(RangeCoder *c){
+    c->range=0xFF;
+    c->low +=0xFF;
+    renorm_encoder(c);
+    c->range=0xFF;
+    renorm_encoder(c);
+
+    assert(c->low   == 0);
+    assert(c->range >= 0x100);
+
+    return c->bytestream - c->bytestream_start;
+}
+
+#if 0 //selftest
+#define SIZE 10240
+int main(){
+    RangeCoder c;
+    uint8_t b[9*SIZE];
+    uint8_t r[9*SIZE];
+    int i;
+    uint8_t state[10]= {0};
+    
+    ff_init_range_encoder(&c, b, SIZE);
+    ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16);
+    
+    memset(state, 128, sizeof(state));
+
+    for(i=0; i<SIZE; i++){
+        r[i]= random()%7;
+    }
+    
+  
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        put_rac(&c, state, r[i]&1);
+STOP_TIMER("put_rac")
+    }
+
+    ff_put_rac_terminate(&c);
+    
+    ff_init_range_decoder(&c, b, SIZE);
+    
+    memset(state, 128, sizeof(state));
+    
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        if( (r[i]&1) != get_rac(&c, state) )
+            av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i);
+STOP_TIMER("get_rac")
+    }
+    
+    return 0;
+}
+
+#endif